PowerSkin today released the PowerSkin case with built-in battery for the Samsung Galaxy series Android phones. The PowerSkin case is a silicone case with built-in rechargeable battery that's 1500 mAh in capacity. The case currently supports the Samsung Galaxy phones, HTC phones, with support for other Droid phones coming soon. Here is more info on this battery case for Android smartphones:

PowerSkins are available in T-Mobile stores along with most major E-tailer sites like Amazon for the Samsung Galaxy S 4G ($59.99), Samsung Vibrant ($59.99), HTC myTouch 4G ($49.99), HTC HD7 ($59.99) and HTC HD2 ($59.99); the Samsung Galaxy i9000 ($59.99) and i3000 ($59.99) are available via international carriers.